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Hiepe, P.* ; Herrmann, K.H.* ; Güllmar, D.* ; Ros, C.* ; Siebert, T.* ; Blickhan, R.* ; Hahn, K. ; Reichenbach, J.R.*

Fast low-angle shot diffusion tensor imaging with stimulated echo encoding in the muscle of rabbit shank.

NMR Biomed. 27, 146-157 (2014)
Open Access Green as soon as Postprint is submitted to ZB.
In the past, spin-echo (SE) echo planar imaging(EPI)-based diffusion tensor imaging (DTI) has been widely used to study the fiber structure of skeletal muscles in vivo. However, this sequence has several shortcomings when measuring restricted diffusion in small animals, such as its sensitivity to susceptibility-related distortions and a relatively short applicable diffusion time. To address these limitations, in the current work, a stimulated echo acquisition mode (STEAM) MRI technique, in combination with fast low-angle shot (FLASH) readout (turbo-STEAM MRI), was implemented and adjusted for DTI in skeletal muscles. Signal preparation using stimulated echoes enables longer effective diffusion times, and thus the detection of restricted diffusion within muscular tissue with intracellular distances up to 100 µm. Furthermore, it has a reduced penalty for fast T2 muscle signal decay, but at the expense of 50% signal loss compared with a SE preparation. Turbo-STEAM MRI facilitates high-resolution DTI of skeletal muscle without introducing susceptibility-related distortions. To demonstrate its applicability, we carried out rabbit in vivo measurements on a human whole-body 3 T scanner. DTI parameters of the shank muscles were extracted, including the apparent diffusion coefficient, fractional anisotropy, eigenvalues and eigenvectors. Eigenvectors were used to calculate maps of structural parameters, such as the planar index and the polar coordinates θ and ϕ of the largest eigenvector. These parameters were compared between three muscles. θ and ϕ showed clear differences between the three muscles, reflecting different pennation angles of the underlying fiber structures. Fiber tractography was performed to visualize and analyze the architecture of skeletal pennate muscles. Optimization of tracking parameters and utilization of T2 -weighted images for improved muscle boundary detection enabled the determination of additional parameters, such as the mean fiber length. The presented results support the applicability of turbo-STEAM MRI as a promising method for quantitative DTI analysis and fiber tractography in skeletal muscles.
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Publication type Article: Journal article
Document type Scientific Article
Keywords MRI; Stimulated echo; STEAM; Turbo-FLASH; Diffusion tensor imaging; Fiber tractography; Muscels; Rabbit shank; Mouse Skeletal-muscle; Human Calf Muscle; Fiber Tracking; In-vivo; Steam Mri; Architecture; Brain; Dti; Motion; Sensitivity
ISSN (print) / ISBN 0952-3480
e-ISSN 1099-1492
Quellenangaben Volume: 27, Issue: 2, Pages: 146-157 Article Number: , Supplement: ,
Publisher Wiley
Reviewing status Peer reviewed